The subject matter disclosed herein relates to data collecting and processing techniques with particular discussion about methods that optimize sampling data rates into fixed-length buffers found on valve assemblies.
Industrial factories and like facilities operate process lines that may include many varieties of flow controls. Examples of these flow controls include pneumatic and electronic valve assemblies (also “control valves”) that regulate a flow of process fluid (e.g., gas and liquid). In conventional configurations, these valve assemblies have a number of components that work together to regulate flow of process fluid through the valve assembly. These components include a stem, a plug, a seat, and an actuator that couples with the stem to change the position of the plug relative to the seat. The components can also include various linkages and springs that ensure proper movement, e.g., of the stem and/or the plug. In some constructions, the valve assembly incorporates a valve positioner with electrical and/or electro-pneumatic components. During operation, the valve positioner instructs the actuator to change the position of the plug relative to the seat. Often, the valve positioner issues the instructions in response to control signals from a controller that is part of a process control system (also “distributed control system” or “DCS”). The instructions are part of management functions in the DCS that can, inter alia, cause the valve assemblies to operate in a manner that achieves the process parameters set out for the process line.
Data collection and analysis plays an important role at these industrial facilities to monitor operation of the devices on the process line. The data can arise from the devices and areas proximate the devices, e.g., by way of sensors that attach to the device and/or piping that couples with the device. The facility can deploy certain data processing techniques that detect the onset of problems in the devices; for example, the techniques can identify changes in operation of a valve that may indicate damage (e.g., wear, corrosion, etc.) to the seat, the stem, the linkage, the springs, the actuator, and other components of the valve.
Facilities often incorporate large data acquisition systems to collect data across wide swaths of devices that are part of the process line. Stand-alone test beds, or “valve testers,” are also available that use sensors and other connections with the devices to gather data during operation in the process line. Some data acquisition can even occur on the device itself, e.g., on valves that are outfit with hardware and electronics to receive, store, and/or transmit data and information that relates to the operation of the valve. This hardware may include a valve positioner, which resides on and/or near the valve and operates the valve to modulate the flow of working fluid. Unfortunately, memory limitations with the microprocessor in the valve positioner often fixes the length of the buffer in memory that holds the data. These limitations can render the buffer too small to hold all of the data for a particular test sample based on, for example, the time between samples, the number of measurements stored for each sample, and the total sampling time. This problem with over-prescribing the buffer, or “overflow,” may be addressed, on the one hand, by adjusting the time between samples so all of the data could fit in the buffer. However, in practice, this variable is often not known.